The present utility model relates to a ducted fan power plant unit of a model airplane, and more particularly to a ducted fan integrated power plant unit having a propeller with central blade wheel.
At present, most ducted fan power plant units of model airplanes adopt a design of a straight duct, i.e. the duct fan and the duct stator outer ring are of a straight line design. Therefore, the diameter or area of the air intake port of the duct fan is equal to that of the air exhaust port of the duct stator outer ring. When the air drawn in by the duct fan is exhausted rearwards after it passes through the duct stator outer ring to the air exhaust port, the acceleration of the air exhaust flow is only proportional to the rotating speed of the engine of the duct fan.
In addition, in the prior art, due to the fact that the diameter of the spinner and the central shaft is relatively large, the area of the air intake port of the fan is reduced, and the model airplane is driven only by the blades of the propeller. When high speed flying is needed, the amount of air admission for combustion of the engine is not enough so that air and fuel in the engine can not be mixed adequately, resulting in a reduced work efficiency. Furthermore, in the structure of the duct stator having an outer ring and an inner ring, an air stream passes through only the space between the outer ring and the inner ring of the duct stator. The air, after passing through the stator guide blades arranged between the outer ring and the inner ring, is exhausted rearwards. In this case, no air flow occurs in the stator inner ring. This region (where no air passes through), is right next and most close to the central region where the engine is located. The result is a disordered air flow will occur in this region, and the air flow speed will be adversely influenced, which leads to a reduction of a propulsive force of the model airplane. At the same time, the surrounding region of the central portion of the engine suffers from poor cooling because no air flows through there, and enough air cannot be supplied for the combustion of the fuel. Thereby the engine cannot achieve good working efficiency and due high rotating speed. Accordingly, the rated power of engine cannot be fully brought into play or properly used.
The drawback of the straight duct design and the insufficiency of cooling capability of the prior art ducted fan power plant unit leads to a significantly reduced ratio of actual power to the rated power of the power plant unit. At the same time, the propulsion of the model airplane in the sky decreases with the decreasing power.
On the other hand, the existing ducted fan system of the model airplane suffers from a relatively complicated structure, and a greater number of components. For example, such unit is generally composed of separated blades of propeller and its retaining ring, stator guide blades of the duct stator and its fixing ring, as well as a hundreds of connectors and fasteners of different types and models, which not only leads to an increase of the weight of the ducted fan power plant unit, but also to an increase number of mounting procedures and to the requirement for a high operation technique. The result is, for most model airplane amateurs and beginners, due to the non-ideal effect in use, many problems will occur in operation and assembly of the model airplane, therefore an improvement is urgently needed indeed.
The purpose of the present utility model is to overcome the above mentioned drawbacks and to provide a ducted fan power plant unit having a propeller with a central blade wheel, the unit has a central blade wheel which can draw air flow at the central portion, and the air drawn-in by the central blade wheel can synchronously function with the air flow of the main blades of the propeller to improve and enhance the quality and the amount or volume of the air blowing.
The technical scheme for realizing the object of the present utility model is: a kind of ducted fan power plant unit with propeller having central blade wheel, it comprises a ducted fan stator, which includes an outer ring, an inner ring, several blade shaped connecting bars which connect the outer ring and the inner ring and which can act as stator guide blades, and a fixing support arranged on one side of the inner ring, in the front portion of the outer ring of the ducted fan stator, a conical air intake guide ring is provided for increasing the intake of air flow, the inner diameter of which is larger outside than inside,
an air exhaust duct, which is connected to the rear portion of the ducted fan stator, the air exhaust duct and the ducted fan stator have a common central axis,
an internal combustion engine having an fuel intake port and a fuel tank having an fuel supplying port, they are mounted one after other on the fixing support and are situated in the air exhaust duct, in addition, the fuel supplying port of the fuel tank is communicated with the fuel intake port of the internal combustion engine through the fuel pipe,
a propeller, which includes several main blades, a conical retaining ring, the conical retaining ring has a central shaft hole and several central conical blades as the blade wheel arranged in the retaining ring, on the periphery of the retaining ring are provided the main blades, the said propeller can be mounted on the power shaft of the engine through the central shaft hole of the retaining ring,
a cap, which is conical and mounted on the end portion of the power shaft and is situated in the center portion of the retaining ring of the propeller so that the central conical blades can be exposed to the outside of the cap, and the spaced guide between two adjacent central conical blades can be communicated with the inner ring opening of the inner ring of the ducted fan stator.
As the above mentioned ducted fan integrated power plant unit having a propeller with central blade wheel, wherein on the inner surface of ducted fan stator inner ring are provided several radial uniformly distributed blade-shaped inner ring guide blades.
As the above mentioned ducted fan integrated power plant unit having a propeller with central blade wheel, wherein the power plant unit further includes a tail cap of the fuel tank, which is mounted on the rear end of the fuel tank.
As the above mentioned ducted fan integrated power plant unit having a propeller with central blade wheel, wherein the outer diameter of the end portion of the main blades is gradually reduced from the front to the rear, and the end portion has approximately the same inclination angle as that of the peripheral surface of the central air intake guide ring.
It can be seen from the above that the propeller of the ducted fan integrated power plant unit having a propeller with central blade wheel according to the present utility model has several main blades and several central conical blades of the blade wheel which operate or rotate synchronously with the main blades to generate a main air stream M and a central suction air stream T respectively, the ducted fan stator has inner ring guide blades, stator guide blades and conically tapered air intake guide ring, hence the amount of air supply can be increased and air flow can be guided to be exhausted rearwards in a straight line manner to prevent from the occurrence of disordered air flow. At the same time, the air flows drawn by the central conical blades can cool the mixed gas in the crankcase of the engine and the density of the mixed gas can be increased, thereby the compression ratio can be increased, and the successful start rate and the propulsive force can be improved or raised. The engine of the ducted fan integrated power plant unit can use conventional two-stroke engine of the model airplane, the engine makes the propeller of the ducted fan power plant unit rotate to draw in air at the front end, and after the air enters the stator through the cone tapered air intake guide ring and passes through the stator guide blades of the fan duct stator, it is exhausted rearwards, so as to join with the central suction or drawn-in air flow of the inner ring of the stator guide blades, then passing through the outlet of the ducted fan stator and the fuel tank in the central position, exhausting rearward air with large volume and at high speed to generate strong propulsive force. The present utility model features also the simple and integrated structure, high efficiency and lightweight.